The preparation of mono-long chain amine oxide surfactants by the oxidation of tertiary amines is of considerable commercial interest. Such surfactants are widely used in commercial cleaning compositions, especially high sudsing dishwashing detergents. Such concentrated solutions are especially useful in formulating concentrated or "compact" liquid detergent compositions which are now favored by many consumers and generally contain lower amounts of water than conventional detergents. However, the formulation of mono-long chain amine oxide surfactants containing high levels, i.e., greater than about 30%, by weight of the amine, has proven to be a difficult problem to overcome. Typically, mono-long chain amine oxide surfactants containing above 30% active result in an unhandleable gel especially when a phase modifying solvent is not incorporated. It has also been discovered that some sources of mono-long chain amine oxide surfactants may be contaminated with residual amounts of nitrite materials, especially inorganic nitrites. Contamination by such nitrites may be tolerable under many circumstances. For some uses however, the presence of nitrites may be undesirable, since they can react with other ingredients which may be present in the fully formulated detergent compositions.
Detergent formulators presumably could arrange for special care to be taken during the manufacture of mono-long chain amine oxides in order to minimize the formation of undesirable nitrite contaminants. However, the manufacturer of high volume, low cost chemicals such as home-use detergents can ill afford surfactants and other raw materials requiring special reaction techniques or special reactants, due to their expense.
The present invention solves the viscosity problems and eliminates the concern about high nitrite/nitrosamine levels normally associated with mono-long chain amine oxide surfactants containing high active levels, i.e., greater than about 30%, by weight of the amine, using simple cost-effective techniques and without the use of phase modifying solvents. The invention herein thus affords access to a concentrated, high quality supply of this class of surfactants.